devel/py-robotframework-pabot: update to 0.18

From Mikko Korpela:

This release fixes one annoying bug that has been there since the beginning of
pabot: suite setups and teardowns were logged only from one of the running
processes. Now it logs them from all - so be prepared for multiple setups and
teardowns in logs.

PR: 202748
Submitted by: vladimir.chukharev@gmail.com (maintainer)